The present invention concerns a machine for producing corrugated board lined on a single face, commonly called "single-face corrugator", and more precisely concerns an apparatus for holding the sheet of paper on the second corrugating roller, termed "lower corrugated cylinder", used on this type of machine.
Corrugating of paper is usually achieved in a single-face corrugator by thermo-forming between two corrugated cylinders heated through their hollow inner space with saturated vapor, and applied by meshing by two actuators. To prevent separation of the corrugated sheet from the second corrugating roller, termed lower corrugated cylinder, it is necessary to provide an apparatus for holding the sheet on this latter cylinder. Prior art holding apparatuses are mechanical in nature and are generally constituted by a set of guiding fingers, or "combs", in contact with the moving corrugated sheet. Such holding apparatuses present a certain number of disadvantages:
mounting and de-mounting of the combs is long and difficult,
because of the presence of the combs, it is not possible to put adhesive opposite each of these,
since the paper permanently rubs against the combs, wear is rapid and maintenance costs are high,
to detach the corrugated paper from the upper corrugated cylinder, the combs have to be engaged in the latter, which makes machine grooves necessary.
Instead of using mechanical holding means, use of pneumatic holding means, either by pressure or by suction, has been considered for some time. However, such means have not been entirely satisfactory, on the one hand because the means for holding by pressure have the disadvantage of blowing away a considerable part of the adhesive laid on the corrugated paper, and on the other hand because the various suction means proposed hitherto either give insufficient suction unless considerable energy is involved, or do not allow heating with saturated vapor of the lower corrugated cylinder to be maintained.